Aircraft utilize navigation devices that provide attitude solutions (e.g., pitch, roll and heading information) along with inertial solutions (e.g., accelerations and angular body rates, which velocity can be determined therefrom) to various displays and systems of the aircraft. Some of these navigation devices are redundant to provide a measure of safety in case of equipment failure and provide for confirmation of correct readings. Dispatch of aircraft also is sometimes dependent upon the availability of redundant navigation devices that provide attitude and inertial solutions. Conventional implementations use multiple devices to provide the redundant measurements.
In many conventional implementations, three Air Data Inertial Reference Units (ADIRUs) are used to provide the redundant measurements. However, there is a desire to replace one of the ADIRUs with a different type of navigation unit, such as a Global Positioning System (GPS)-aided Attitude Heading Reference System (AHRS). While making this transition, there is also a desire to be able to dispatch if one of the ADIRUs fails. However, if the remaining ADIRU and GPS-aided AHRS calculate two independent dissimilar attitude solutions, two independent dissimilar inertial solutions or both, it cannot be determined whether the remaining ADIRU or the GPS-aided AHRS is calculating the erroneous attitude solution.
For the reasons stated above and for the reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for improved systems and methods for determining an erroneous attitude error in a system that utilizes a combination of different types of navigation units.